Abstract The effects of convective heat transfer by hydrothermal fluid flow on fission-track (FT) thermochronology are studied using numerical modelling techniques. Parameter studies are carried out on two-dimensional crustal segments with a steeply dipping fault zone exposed to constant denudation to evaluate the relative importance of different variables, including denudation rate as well as hydraulic and material properties. Time–temperature histories of particle points are calculated in the vicinity and also a few kilometres away of the fault zone. These time–temperature paths are then used in a forward-modelling approach to determine the expected FT cooling ages and track-length distributions. Modelling results indicate that hydrothermal fluid flow can significantly disturb the background conductive thermal state of the upper crust, and the interpretation of FT data using a steady-state geothermal gradient can result in erroneous denudation rates that overestimate the true erosion rates by more than 80%. A pattern of highly varied FT cooling ages from samples at the same elevation does not necessarily ask for differential tectonic movements, instead it can be generated by deep circulation of groundwater within a few million years (Ma). Denudation rates inferred from FT cooling age–elevation plots are likewise inaccurate in a hydrothermally active area because the important assumption about closure temperature isotherms being horizontal or at a constant depth below the surface is not met.

Abstract The Jurassic System (199.6-145.5 Ma; Gradstein et al. 2004 ), the second of three systems constituting the Mesozoic era, was established in Central Europe about 200 years ago. It takes its name from the Jura Mountains of eastern France and northernmost Switzerland. The term ‘Jura Kalkstein’ was introduced by Alexander von Humboldt as early as 1799 to describe a series of carbonate shelf deposits exposed in the Jura mountains. Alexander Brongniart (1829) first used the term ‘Jurassique', while Leopold von Buch (1839) established a three-fold subdivision for the Jurassic (Lias, Dogger, Malm). This three-fold subdivision (which also uses the terms black Jura, brown Jura, white Jura) remained until recent times as three series (Lower, Middle, Upper Jurassic), although the respective boundaries have been grossly redefined. The immense wealth of fossils, particularly ammonites, in the Jurassic strata of Britain, France, Germany and Switzerland was an inspiration for the development of modern concepts of biostratigraphy, chronostratigraphy, correlation and palaeogeography. In a series of works, Alcide d'Orbigny (1842-51, 1852) distinguished stages of which seven are used today (although none of them has retained its original strati graphic range). Albert Oppel (1856-1858) developed a sequence of such divisions for the entire Jurassic System, crucially using the units in the sense of time divisions. During the nineteenth and twentieth centuries many additional stage names were proposed - more than 120 were listed by Arkell (1956) . It is due to Arkell's influence that most of these have been abandoned and the table of current stages for the Jurassic (comprising 11 internationally accepted stages, grouped into three series) shows only two changes from that used by Arkell: separation of the Aalenian from the lower Bajocian was accepted by international agreement during the second Luxembourg Jurassic Colloquium in 1967, and the Tithonian was accepted as the Global Standard for the uppermost stage in preference to Portlandian and Volgian by vote of the Jurassic Subcommission ( Morton 1974 , 2005 ). As a result, the international hierarchical subdivision of the Jurassic System into series and stages has been stable for many years.

Abstract The Carboniferous (359.2–299 Ma, Gradstein et al. 2004 ) succession of Central Europe records one of the most important time periods with respect to European geology, since it marks the final collision of Gondwana with the northern continent of Laurussia (i.e. Laurentia, Baltica and Avalonia). Oblique convergence resulted in collisional processes which created a mountain belt extending from Russia, through western Europe and into North America. The climax of the Variscan Orogeny was the formation of the supercontinent Pangaea leaving a relict Palaeo-tethys to the east ( Scotese & Langford 1995 ) (Fig. 9.1 ). The Variscan belt is a broad (c. 1000 km) complex curvilinear feature extending across Europe and marking the zones of Variscan-age deformation (Figs 9.2 & 9.3 ). The final phase of Variscan activity was also a period of terrane mobility and tectonic instability in the Central European region with sinistral wrench faulting causing widespread rifting of the northern European crust ( Pegrum 1984 a, b ; Ziegler 1990 ). The Carboniferous succession in Central Europe is generally dominated by marine sediments (both clastic and carbonate) in the lower part of the succession¨ The clastic sediments tend to be deeper-water shelf or turbiditic successions, although in some areas (e.g. Belgium, northern Germany) limestones are locally important or even dominant, particularly during the Tournaisian and Visean. In late Carboniferous times, successions are predominantly continental with some coal-bearing units being deposited (particularly in Westphalian times). An exception to the dominantly sedimentary record is provided

Abstract The Permian (299-251 Ma; Wardlaw et al. 2004 ) succession of Central Europe records the change from a Pangaea configuration and compressive tectonic regime inherited from the Variscan Orogeny, to the development of the broad thermal subsidence-controlled Southern Permian Basin and its inundation by the Zechstein Sea. During latest Carboniferous-Early Permian times, the final phase of Variscan orogenic extension produced a series of small strike-slip and extensional continental basins across central and western Europe. Within these basins Stephanian and Lower Rotliegend continental successions were deposited. Subsequent thermal subsidence led to the gradual coalescence of these isolated basins to form the large Southern Permian Basin which extended across much of central and western Europe (Fig. 10.1 ). Early Permian sedimentation was predominantly fluvial and lacustrine, changing later to aeolian. This change was due either to a significant climate change, or the result of a decline in relief of the surrounding uplands. By the end of the Early Permian extensive dunefields occupied the basin margins with saline lakes (playas) in the basin depocentres ( Verdier 1996 ). A regional, possibly glacio-eustatic, rise in sea level later in Permian (Zechstein) times resulted in the rapid flooding (from the north) of the Southern Permian Basin. The Zechstein succession comprises a series of evaporitic cycles, and associated carbonates and muds, reflecting progressively greater evaporation and the shallowing either of the whole basin or the margins of the basin. There has been a considerable amount of interest in the Permian in recent years, with a number

Abstract: A three-dimensionally preserved skull and parts of the postcranial skeleton of an ichthyosaur ( Leptonectes ) was found vertically oriented within on-average slowly deposited (0.5 m/My) Lower Jurassic shallow-water marls. The ichthyosaur sank headfirst into the seafloor because of its center of gravity, as anatomically similar comparably preserved specimens suggest. The skull penetrated into the soupy to soft substrate until the fins touched the seafloor. There is no evidence either for active penetration of the ichthyosaur during death agony or an acceleration by explosive release of sewer gas that would have pushed the skull into the substrate. Ichnofabrics and crosscutting relationships among trace fossils preserved therein allow analysis of stratigraphic completeness. In spite of on-average slow accumulation, the ichthyosaur-hosting sediments formed rapidly during three distinct but similar deposition-bioturbation phases. First, 10 to 15 cm of mud accumulated rapidly. Biodeformational structures subsequently produced therein imply a soupy consistency. As sedimentation slowed down, muds slightly dewatered and consolidated, as reflected by trace fossils with distinct outlines (Palaeophycus and Planolites, thereafter Thalassinoides and Chondrites). The contact with the overlying depositional interval is obliterated by biodeformational structures. Hence, the previously rapidly deposited mud must still have been soft. A short time after the third deposition-bioturbation phase, the ichthyosaur parts penetrated into the still-soft mud and started to be degraded microbially. Below the bioturbated zone, but before compaction, a concretion started to form around the ichthyosaur parts and led to their excellent preservation. During further burial, the skull-hosting concretion experienced differential compaction and moved downward relative to the underlying beds. The skull-hosting concretion penetrated through condensed deposits representing three ammonite zones. Restoring differential compaction, the initial porosity of the sediment can be estimated to have been > 70%. Compared to modern analogues, such muds are soft, as ichnofabrics imply.